Solid-to-Solid Crystallization of Organic Thin Films: Classical and Nonclassical Pathways

Abstract

The solid-to-solid crystallization processes of organic molecules have been poorly understood in view of the complexity and the instability of organic crystals. Here, we studied the crystallization of a π-conjugated small molecular semiconductor, bis-(8-hydroxyquinoline) copper (CuQ 2 ), by annealing the thin films at different temperatures. We observed a classical film-to-nanorods crystallization at 80 °C, a coexistence of classical and nonclassical nucleation and particle growth at 120 °C, and a nonclassical crystal growth at 150 °C. We found that the growth of the crystals followed the following processes: particle nucleation, particle growth, particle migration, nondirectional particle attachment, and structure reconstruction. We notice that the growth of CuQ 2 particles follows an outside-to-inside process. More interestingly, our experiments suggest that the submicron CuQ 2 particles are able to migrate dozens of micrometers at 150 °C.

Dye-sensitized solar cells strike back

“…Energy levels can be varied by modifying the ligand or metal center. 485,[487][488][489] Although liquid DSCs have greatly benefited from the implementation of transition metal complexes as electrolytes, as they are far more efficient and less corrosive than iodide/triiodide, only a handful of new compounds of this class have been tested in solid state DSCs so far. 284,286,320 Despite this, the best-performing ssDSCs are those employing a metal complex as the hole conductor (see Table 7).…”

A Highly Proton-Conductive 3D Ionic Cadmium–Organic Framework for Ammonia and Amines Impedance Sensing

“…9 MOFs are used as a new intriguing class of templates, which can be designed into diverse types of chemoresistive gas sensors. 10−12 Ammonia and amine sensors gradually developed from semiconductors, 13 inorganic/organic thin films, 14 conducting polymers, 15 and nanocomposites. 16 Representatively, Campbell et al developed an electrically conductive 2D Cu-based MOF that exhibited excellent NH 3 gas sensitivity.…”

“…Chemoresistive gas sensors have lately received considerable interest owing to the increasing demand for monitoring harmful gases including ammonia, sulfur dioxide, carbon monoxide, NO x , and so on . MOFs are used as a new intriguing class of templates, which can be designed into diverse types of chemoresistive gas sensors. − Ammonia and amine sensors gradually developed from semiconductors, inorganic/organic thin films, conducting polymers, and nanocomposites . Representatively, Campbell et al developed an electrically conductive 2D Cu-based MOF that exhibited excellent NH 3 gas sensitivity .…”

The researcher's guide to solid-state dye-sensitized solar cells

“…277,278 However, they have the tendency to form crystalline domains in the solid state, either immediately upon deposition or over time. 107,279 This crystallization may modify film morphology, worsening the contact between the dye or counter electrode and HTM, thus hindering charge transport; or it may create charge recombination sites at grain boundaries. Metal complexes have already contributed greatly to the advancement of liquid DSCs by replacing iodine/iodide as the electrolyte as they have simple, one-step oxidation and reduction processes (thus reducing the driving force needed for regeneration) and are much less corrosive than the latter.…”